If it helps, I have both a 990 and PF60, and the trigger works fine for me.

You've probably already done this, but have you double checked the trigger switch setting on the back of the PF60?

I love the PF60. I had been using an older Panamax unit, but there was always a slight hum coming from my amps. The PF60 has pretty much solved the problem.

Good luck,

Scott